Wednesday, August 29, 2012

dream science?

Too many entries - let this be the last one for August.

Fantastically, incredibly, unbelievably, implausibly, Monday night I had a dream that directly relates to Monday's entry. I'll leave out irrelevant details: I dreamed that I was experiencing a migraine aura.

In the dream, I noticed the phosphene-like foveal scotoma, and at first had the "is it an afterimage? what bright light did I look at?" reaction, and then realized what it really was. It was upsetting, actually, because the last one was just 1 week previous, and I felt like once a week is a bit too frequent.

I then set about trying to record the aura with my perimetry program, except that my computer was now a large, flat panel lying on the floor, like a giant i-pad. The layout was of course different - not a blank gray screen, but a thin-line black grid, like a Go board, on a wood-brown background. Jingping was there, and kept trying to move the grid around, and I kept telling her to stop.

Once I was trying to record it, the scotoma was no longer foveal, but extended 10-20 degrees out, straight to the left and then arcing downward towards the inferior vertical meridian. This makes me think that I wasn't actually experiencing an aura in my sleep - to get from the foveal scotoma to 10-20 degrees should take 15-20 minutes, and I don't think that much time actually passed in the dream - it seemed like less than a minute. Of course, time and space are both funny in dreams, so who knows. There was no headache on Tuesday, anyways.

It was very frustrating trying to set the fixation point in the dream perimetry program. I just couldn't fixate - I would set it in one place, and then felt that it should be somewhere else. I think I finally gave up and started sticking my hand in the scotoma to probe its size.

So, whether or not I was really experiencing an aura, or just dreaming that I was experiencing one, is an interesting question. It seemed like a real one, and I noted lots of spatial details: the tiny phosphenic bead of the foveal scotoma, the fuzzy noisiness of the peripheral scotoma arc (though the periphery seemed clearer somehow in than true peripheral vision), the thin black lines of the perimetry grid, the unfixable fixation spot.. If visual experience includes V1 activity, and if the visual aura occurs in V1, and if V1 is quiet or suppressed during dreaming, how could I have seen what I did, unless spatial vision includes a good deal of higher-level inference?

It seems that I proposed an experiment on Monday afternoon, and then did the experiment in my sleep that night. I have never been so efficient!

Monday, August 27, 2012

summation or conclusion?

So, I'm realizing now that this note from a few days ago is touching on this entry from several months back (if only I could keep everything in my head at once...). In the latter, I was talking about the idea that visual experience is a stack of phenomena, extending all the way down to the optical image, even to the light field, and all the way up to cognition and emotion. In the former, I realized that my standing, computational interpretation of the classification image experiment involves an assumption that estimates of a particular psychological construct - perceived contrast - are mediated by the same processes whether the stimulus is simple or complex.

This stance doesn't conflict with the 'stack' idea, but when you think of both together it seems dubious. With simple stimuli, there isn't much else elicited by the visual pattern, so estimates of its properties can be localized to a small set of possible mechanisms, which is the point of using simple stimuli in the first place. So, there are multiple layers to the stack, but most of them are relatively empty or inactive. When the stimulus is complex, all those other stacks are now active, and filled with activity which is ostensibly more important and interesting to the observer. Is it reasonable to continue to assume that the observer can make use of the same information in that 'spatial vision' layer that he could when there was nothing to distract him elsewhere?

I realized this connection because I was thinking of the implications of one alternative (complex visual qualia are the result of highly nonlinear summation of simple visual qualia) or the other (complex qualia may be inferences drawn from 'basis' qualia, that could possibly exist - as perhaps in a dream - independently of those bases). How do you tell the difference? Take away the spatial vision level, and see what is left. How to do this? Lesions maybe, but the first thing that comes to mind is to compare what imagery looks like when you're seeing it versus when you're dreaming it.

Friday, August 24, 2012

punched in the head

title says it all. punched a few times in the head, and now i have a headache. feels migrainish. it is possible that getting punched in the head in just the right way can trigger a migraine. or maybe i have a concussion? i do have a big red bruise on my forehead, so maybe the pain is on the outside, muscular, and i just can't tell the difference since it's all just front-of-the-head.


**edit, 0:23, 8/27/12
the bruise is still there, fading, and the flesh is a bit tender - worse yesterday - but the headache was gone when i woke up saturday morning.

Thursday, August 23, 2012

vacation report

Spent the last 5 days (Sat-Wed) down in Tennessee/Alabama, visiting family. Monday morning, Jingping woke up about 8 and went looking around and came back saying that my parents were still home, when she thought they should be out taking a walk somewhere. I was barely awake, still hadn't opened my eyes. When I finally did a few minutes later, I found that I was halfway through a scintillating scotoma, maybe around the 15-20 minute point. It looked a lot like last time, left field, relatively straight scotoma from above fixation leftward, arcing downward and below. I got out of bed and went to sit in the sunroom to watch the rest of it. The scintillation was rather weak, but still noticeable - I knew what was happening within a second or two of opening my eyes. The headache started soon after I got out of bed, and was kind of a bad one. Above-behind my eyes, focused on the right side. Nauseated and dizzy for a day, which sucked because I had to drive down to Huntsville Monday afternoon (in my parents' Prius with an expired Kentucky driver's license, don't tell my mother). Still hurt a bit Tuesday night.

I think that maybe the slight headache I described on the 16th might have been part of the prodrome for this one, otherwise I didn't notice any signs.


Last night on the way home I had an insight into how to explain the low-pass gain control that I'm proposing. A basic Barlow-Foldiak type anti-Hebbian learning rule should develop low-pass weights if a set of scaled filters is repeatedly exposed to low-pass input, or maybe even if it's just exposed to white noise. Gonna try this later today!

Friday, August 17, 2012

contrast or inference?

Norma Graham makes an interesting point, which I've seen quoted many times, in her book on spatial vision. She notes that it is as if the brain is transparent to what is happening in the early levels of visual processing, and that this is curious. It's curious, but it's a typical stance for someone who studies spatial vision; we assume that discrimination or identification or detection of signal strength is mediated almost entirely by the filters that are transducing the signal, not those that understand it, or respond (overtly) to it.

Whether or not this transparency holds when complex images are viewed is, I think, totally unknown. It may be that the percept elicited by a complex scene really is the sum of its parts, and that it simply provokes additional sensations of meaning, identity, extension, etc., which are tied to spatial locations within the scene. So, the visible scene that we are conscious of is indeed an object of spatial vision. This is the point of view I generally adopt, and I think it is common.

Another view is that the percept is entirely inference. Boundaries, surfaces, colors, textures, etc., are qualities in themselves, inferred from particular organization of spatial structure, and these then are organized in such a way that objects and identities and meanings can be inferred in successive stages. These inferences are what is seen consciously; perhaps inferences, and the evidence for them (the matter of spatial vision), are experienced simultaneously, but the substantive inferences, being the important elements of experience, are what dominate consciousness. So, only a small part of the phenomenal scene is actually constituted by e.g. luminance contrasts, and much more of it is constituted by higher level inferences. I think this point of view is also common, maybe especially in the current generation of visual neuroscientists.

The latter view is not exclusive of Graham's observation. If the patterns that are viewed are simple enough, they will not form objects, and will not have meaning. Or, they will be interpreted only as what they are, which doesn't require much inference, or only circular inference (which isn't a bad thing necessarily, when you really do want to conclude that a thing is itself, e.g. a gaussian blob of light, on the basis of its being a blob of light; usually, you want to infer that there is a letter on a page on the basis of a particular arrangement of blobs of light).

So, in the experiment that I'm currently analyzing to death, I am clearly taking the first view, in which case I think my conclusions are solid. If the second view is more accurate, what does the result mean? It could mean that inferences about image strength are based on higher frequencies just because they are the more susceptible to loss in a weak signal. If I'm asking subjects to judge image contrast, they could easily interpret this as judging image strength, and then their judgments would be biased towards the most delicate parts of the image, but they would still take everything into account.

This latter interpretation is still interesting, but it doesn't require "suppression". It is worth mentioning and I should at least include it in the manuscript, although the FVM talk probably will not have space... already there's barely space for the default story.

Thursday, August 16, 2012

nausea, photophobia, headache

woke up slightly late today, started to feel sick on the train; slightly nauseated all day long (mainly manifesting as excessive salivation, gross), a bit of photophobia. might be eyestrain or due to my crooked (broken, $10) glasses. briefly on tuesday night inverted the contrast on firefox, but then switched it back. at the time it was because my glasses seemed smudgy and i just couldn't get them clear, thought, "ah, it's a sign!", but decided no, it's the glasses. right now definitely a slight headache. as usual in my forehead, just above my eyes, maybe a bit left of center.

quick note

Something I've been meaning to write a note on for a while. Even as I write this, I don't have the idea quite in my head.

What is it about apparent contrast that is interesting, as opposed to sensitivity? By most measures, they're the same thing. If I ask someone to do an experiment where they have to discriminate between one contrast and another, I'm assuming that they are doing some mental comparison between two apparent contrasts, or memories of two apparent contrasts. By varying the physical difference between the two contrasts, I can then quantify the person's performance on this task, e.g. the difference at which they can no longer measurably discriminate. These are the sorts of measurements that are usually made in psychophysics.

These performance measures are understood to reflect the subjective, phenomenal properties of interest. But they involve a nearly unsolvable confound: we can't tell what part of the discrimination is due to relative internal response strength and what part is due to internal noise.

So to me, measuring apparent contrast is a way at getting around this problem. You get to measure, directly, the internal response to the stimulus. The new problem, then, is in quantifying what you've measured. The reverse correlation experiment that I did, I realize now, was cognizant of all this, but it was subliminal for me. The experiment is not measuring performance, but it is very similar to an experiment that would be measuring discrimination performance. In this experiment, the stimuli are always easily discriminable, so there are no limits to measure. The subject is asked to discriminate between the strengths of the two stimuli, but I measure no interval or reliability of this discrimination. This is because there is no objective stimulus strength.

The purpose of the experiment is to find out what constitutes stimulus strength when strength is defined, to an observer, as luminance contrast. What I get back is (no matter how I measure it) a description of what components count more or less than other components in making decisions about stimulus strength. I then test a bunch of plausible models to see whether they might also count components in similar ways. Lucky for me, only a particular type of model works, so I can make a sort of conclusion from the study.

So, apparent contrast is the way things look, and then behaviors can be carried out on the basis of how things look. Most visual psychophysics directly analyzes the behaviors that are based on appearances. I've tried to directly analyze the appearances themselves. Did I succeed?

Monday, August 13, 2012

unifications of china 1

Random idea from this weekend: create a set of spatiotemporal maps illustrating the unifying conquests of China. For fun. Let's make a list:

1. Qin: Ying Zheng and Guanzhong
Qin was one of many Warring States in the centuries leading up to the first true unification of China in 9780HE. Qin was based in the area around and to the west of Xi'an, which is protected by mountain ranges and accessible only through narrow passes (I traveled through the Hangu pass to visit Xi'an in 12010HE): hence the region's name of Guanzhong, "within the passes". The conquest has an ill-defined starting point, since the different states had been in contention for centuries. However, it was with Ying Zheng's rule that most of the work was done: between 9771 and 9780, China proper went from seven states to one. This period, the Qin Unification War, could be taken as the first.

2. Han: Liu Bang and Guanzhong
Qin didn't long outlive Ying Zheng, who died in 9791. Soon after his death, Qin was overthrown and broken up into a number of kingdoms, united in theory by the Emperor of Chu, who was in fact a puppet of the warlord Xiang Yu. Xiang Yu's confederation quickly disintegrated into civil war between Xiang's Chu state and Liu Bang's Han state, which lasted from 9795 to 9799, when Chu was finally defeated and absorbed into Han. Han, by the way, based its power in the mountain-protected cities of Hanzhong and Chang'an, as Qin had done. Xiang Yu had placed his capital in Pengcheng, in eastern China. This war, and its result, was messy: at any given point in time, even for a decade after the war ended, it was unclear just who was in charge of particular regions, and a lot rested on the proclaimed allegiances of one or another warlord. However, there are standard interpretations of who was with who and when, that could be used to clarify an illustration.

3. Wei/Jin: Cao Cao and Guandong (east of the passes)
Han lasted for 400 years. When it finally collapsed around 10190, there were more than 20 years of war, followed by a half-century period of fracture into the Three Kingdoms of Wei, Wu, and Shu. The Wei state, based in the western edges of the central plains, just east of the mountain strongholds favored by Qin and early Han, eventually conquered Shu in 10263, was replaced in a coup by Jin in 10265, and finally conquered Wu in 10280. After this, Jin slowly fell apart, and China wouldn't be put together under one government again for another four centuries. The Wei/Jin unification was so slow, taking more than 80 years, that it can't really be considered a 'conquest'; it was a slow succession of local wars, with long spaces of quiet in between. I don't think this one would count.

I don't know much about the establishment of Sui - we'll wait until I've read a bit more on it before I continue.

Wednesday, August 08, 2012


Yes, so my glasses broke about 2 weeks ago. I explained it already in the July 24 post.

I still don't have my new pair. Should be here any day now. I'm wearing a 10-year old pair, over-negative in both eyes, but only at night to watch the Olympics and "work" on my laptop. Otherwise I need to be within 12 inches or so to see clearly.

At distance, my acuity is no better than 20/200. I can tell just by looking into the distance and sticking a finger out: no detail that I can see is much smaller than maybe a quarter of the thickness of a fingernail (a little bigger than a degree). So, my acuity limit is probably not much more than 4cpd.

If this was the best I could do, I would be on the bad end of low vision. But it gets better the closer you get to my face (come on, get closer to my face) - like I said, everything is sharp and clear within a foot or so. But, at distance - which is how I spend a lot of my commuting time, at least, and a lot of time at taekwondo - I'm 20/200. How bad is that?

For one thing, 4cpd is about the acuity limit of a cat (or of some jumping spiders). So it's not bad on a basic vision standard, because cats and jumping spiders are very visual creatures. 4cpd is good enough to get by on vision. But for a human, in the world of humans, it's not too good. At distance I can't recognize faces, at all. Ten days' practice, and I just can't do it if I don't have some other information, and then I don't think it counts. I can't read signage - I can't tell what trains are coming into the station at Government Center. None of that is debilitating, but it makes sense to call it a handicap. High frequencies aren't just details, they're content.

20/200 is resolvable detail of 10 minutes of arc. At 35cm, about where my laptop screen is right now, 10ma is about 1mm, which sounds small. But the dot pitch (vertical/horizontal pixel separation) on my screen is about .227mm. With my corrected acuity being around 20/15, I should be able to see details at least as small as 1ma, about .1mm apart, so I can discriminate individual pixels with my normal acuity. At 20/200, I wouldn't be able to discriminate details smaller than 4 or 5 pixels across; I would definitely not be able to read this text (whose lines are 1 pixel thick, and which tend to about 10x5 pixels HxW).

Printed text, which I like to hold pretty close to my face, at least 20cm, would still be unreadable. I'd have to hold it much closer, where the shadow of my head would start to get in the way. I'd need large print. I wouldn't be able to read music. I'm wondering how much acuity you need to do the classic threading of a needle (I haven't even started to wonder about depth perception - I noticed that it was off for the first few days, but I seem to have adapted pretty well, and I'm not afraid to cross the street as I was at the start), or to slice meat and vegetables without slicing yourself - it's not the same as reading, since you're looking for centroids for those things, but I wouldn't really want to try...

Not that I'm going to try, but I could: visual acuity at about 20 degrees eccentricity is close to 20/200. There you have to contend with crowding, though, so you're effectively worse off.

So 20/200 isn't disabling, but it does prevent you from accessing all sorts of primate-relevant stuff. Faces, reading, music, fine finger-based activities. It's been interesting, but I'm just about ready for my new pair of ($10!!) glasses to arrive.

Thursday, August 02, 2012


very slight headache lately. nothing obvious beforehand - maybe some occasional false-alarm-foveal-scotoma feelings, but nothing ever showed up.

those false alarms: when reading, i get a feeling that the text is smudged or jumbled, but when i try to see what's wrong, even one eye at a time, i can't actually find any defects. at other times, it's less clear, because the non-text world is more complicated, but i still haven't actually caught and analyzed any of these defects. so, i still don't know if they're false starts, like a CSD bubble that stops soon after is starts, or just high-level false alarms, i.e. paranoia.

anyways, that's it. working on text for a talk next month. tiny bit of writing lately. somehow i have three people reviewing the classification image manuscript. need to get back to the blur adaptation revision sooner rather than later. not looking forward to it, but once i'm into it i think it should be okay.

Wednesday, August 01, 2012

i know this is stupid

I'm dusty,
I'm crusty,
I'm Augusty!
you're crusty,
you're lusty,
you're Augusty!
she's lusty,
she's busty,
she's Augusty!
you're busty,
you're trusty,
you're Augusty!
we're trusty,
we're gusty,
we're musty,
we're Augusty!
we're Augusty.
we're Augusty.